Activate or Wait – 001

46-year-old male with one hour of central crushing chest pain. Background of hypertension, morbidly obese and a heavy smoker.

We are four minutes from your tertiary centre.

Would you activate your cath lab/STEMI protocol?

ECG interpretation

Evolving anteroseptal occlusion myocardial infarction (OMI)

  • ST elevation and hyperacute T waves in leads V1-3
  • Reciprocal inferolateral ST depression
  • Note the widening of the proximal portion of T waves in V1-2 — remember, infarction causes wide, bulky T waves with increased area under the curve
  • Sinus tachycardia is likely secondary to pain and ischaemia

Given proximity to arrival, no activation call was made. The cardiology team met the patient on arrival and a second ECG was performed:

Activate or wait ECG 2606 2 LITFL
What is your interpretation?

Anteroseptal STEMI

  • Previously seen ST elevation in leads V1-3 is now significantly more pronounced, meeting traditional “STEMI” criteria
  • Inferolateral ST depression is more prominent

ST elevation in aVR adds little diagnostic value here. It is most likely a reflection of diffuse subendocardial ischaemia, due to a combination of evolving infarction, tachycardia +/- hypotension (we are not given a blood pressure). Although infarction of the basal septum can cause ST elevation in aVR, we already suspect the above changes are secondary to left anterior descending artery (LAD) occlusion.

Take a deep dive into the misnomer of ST elevation in aVR.


This patient was taken for emergent angiography.

Key Finding:

Occluded proximal LAD


  • Left Main Coronary Artery – Normal
  • Left Anterior Descending Coronary Artery – Occluded proximally. Type III vessel.
  • Left circumflex coronary artery – Large calibre vessel. Co-dominant. Mild irregularities.
  • Right coronary artery- Small calibre vessel. Co-dominant. Mild diffuse disease.


  • Single vessel coronary artery disease. Occluded LAD.
  • Proceeded to percutaneous coronary intervention to LAD.


  1. Dual antiplatelet therapy – aspirin 100mg + ticagrelor 90mg BD for 12 months. Aspirin 100mg daily for life
  2. Ongoing aggressive cardiovascular risk factor management
  3. Smoking cessation
  4. Admit CCU
Clinical Pearls
  • ST elevation can be subtle in the early stages of occlusion myocardial infarction. Always examine closely for ST depression and wide, bulky T waves. Remember, area under the curve is more important than overall height in hyperacute T waves
  • ST elevation in aVR is simply a reciprocal change to widespread ST depression resulting from subendocardial ischaemia. Always consider non-cardiac causes (hypotension, hypoxia)


Further reading

Online resources


EKG Interpretation

MBBS (UWA) CCPU (RCE, Biliary, DVT, E-FAST, AAA) Adult/Paediatric Emergency Medicine Advanced Trainee in Melbourne, Australia. Special interests in diagnostic and procedural ultrasound, medical education, and ECG interpretation. Editor-in-chief of the LITFL ECG Library. Twitter: @rob_buttner

Dr Amro Sehly LITFL author cardiology

MBBS (Hons), BMSci (Hons). Cardiology Registrar at Royal Perth Hospital in Perth, Australia. Graduate of The University of Western Australia in 2016 with Honours and completed Basic Physician Training with the RACP in 2021. Passion lie in cardiac imaging and electrophysiology.

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